Thermal ablation of the interior lining of a body organ is a procedure which involves heating the organ lining to a temperature that destroys the cells of the lining tissue. Such a procedure may be performed as a treatment to one of many conditions, such as menorrhagia, which is characterized by chronic bleeding of the endometrial tissue layer of the uterus. Existing methods for effecting thermal ablation of the endometrial lining tissue include circulation of heated fluid inside the uterus (either directly or inside a balloon placed in the uterus), laser treatment of the lining, and resistive heating using application of RF energy to the tissue to be ablated. Techniques using RF energy provide an RF electrical signal to one or more electrodes in contact with the subject organ tissue. Electrical current flows from the electrodes and into the organ tissue. The current flow resistively heats the surrounding tissue. Eventually, the heating process destroys the cells surrounding the electrodes and thereby effectuates ablation.
U.S. Pat. No. 6,508,815 (Strul et al.) and U.S. Pat. No. 6,813,520 (Truckai et al) describe a system and method for endometrial lining tissue ablation using an electrode carrying member to transmit radiofrequency (RF) energy to cause thermal heating and, thus, ablation of the tissue, wherein the electrode carrying member is substantially absorbent or permeable to moisture and gases such as steam, and is expandable to conform to the uterine cavity. A suction (aspiration) lumen is positioned within the electrode carrying member to aid in the removal of moisture, whether gas or liquid, present or generated during the ablation procedure. The electrode carrying member comprises an array of electrodes on its outer surface, the electrode array being configured for contacting the endometrial lining tissue in order to deliver energy sufficient to produce ablation to a predetermined depth. The electrode carrying member is collapsed and introduced into the uterine cavity, and then expanded within the uterine cavity so that the electrode array contacts the endometrial lining tissue to be ablated. An RF generator is used to deliver RF energy to the electrodes and to thereby induce current flow from the electrodes through the endometrial lining tissue. As the current passes through and heats the endometrial lining tissue, moisture (such as steam or liquid) leaves the tissue causing the tissue to dehydrate. However, the moisture permeability or absorbency of the electrode carrying member allows for moisture to leave the ablation site through an aspiration lumen of the ablation device to a waste collection receptacle located external to the patient, so as to prevent the moisture from providing a path of conductivity for the current that bypasses (i.e., short-circuits) the conductive pathway through the tissue.
The systems, devices and methods disclosed and described in U.S. Pat. Nos. 6,508,815 and 6,813,520 are well-suited for performing endometrial tissue ablation procedures, e.g., for treating Menorrhagia, the medical term for excessively heavy menstrual bleeding, and are embodied in the NovaSure® endometrial ablation system manufactured and distributed by Hologic, Inc., based in Bedford, Mass. U.S. Pat. Nos. 6,508,815 and 6,813,520 are hereby fully incorporated by reference.
U.S. Pat. Pub. No. 2011/0118718 also describes a system and method for endometrial RF ablation. This system uses an energy delivery device having a dielectric wall capable of non-expanded and expanded shapes, and having an indicator mechanism operatively coupled to the dielectric wall to indicate a dimension of the uterine wall. U.S. Pat. Pub. No. 2011/0118718 is hereby fully incorporated by reference.
FIGS. 1A-B illustrate an exemplary Novasure® endometrial ablation system 100. The ablation system 100 includes an expandable RF applicator head (electrode carrying member) 102, an introducer sheath 104, an introducer tubing 108, and a handle 106. The RF applicator head 102 is collapsed and slidably disposed within the introducer sheath 104 during insertion of the device into the uterine cavity via the introducer tubing 108 (FIG. 1A). The distal end of the sheath 104 is positioned within the uterus, and the handle 106 is manipulated to extend the RF applicator head 102 out an open distal end of the sheath 104 (FIG. 1B), and to expand the RF applicator head to conform to the uterine cavity (FIG. 2). As best seen in FIG. 2, the RF applicator head 102 includes a moisture permeable (woven) mesh electrode array 102a, and an underlying deflecting (i.e., expanding) mechanism 102b used to expand and tension the mesh electrode array 102a within the uterine cavity to facilitate contact between the endometrial lining tissue and the mesh electrode array 102a. The deflecting mechanism 102b includes a pair of metal ribbon flexures 124 extending distally and laterally out the introducer tubing 108 on opposite sides of a co-axially disposed pair of hypotubes 120 and 122 that also extend from tube 108. Non-conductive threads 148 extend from the inner hypotube 122 and have distal ends attached to internal flexures 136 that extend laterally and longitudinally from the exterior surface of hypotube 122.
As seen in FIG. 3A, a respective plurality of longitudinally spaced apart apertures 126 are formed in each flexure 124, which allow moisture in the uterine cavity to pass through the flexures and be drawn into the open distal end of the outer hypotube 120 by a vacuum source 552 fluidly coupled to the inner lumen of the hypotube 120. As seen in FIG. 3B, each flexure 124 includes conductive regions formed by isolated strips of metallic (e.g., copper) tape 128 that are electrically coupled to the array 102a for delivery of RF energy to the endometrial lining tissue. Anode and cathode conductors (not shown) are electrically coupled to respective ones of the strips 128, and extend through the tubing 108 (seen in FIG. 2) to an electrical cord 130, which may be operatively connected to an RF generator 550 (seen in FIG. 1A). During use, one strip 128 on each conductor is electrically coupled via the conductor leads to one terminal on the RF generator while the other strip is electrically coupled to the opposite terminal, thus causing the electrode array 102a on the applicator head 102 to have regions of alternating positive and negative polarity. Since it is important to have proper alignment and electrical contact between the conductive regions of the flexures 124 (e.g., copper strips 128) and electrodes 118a-118d (FIGS. 4A-B) strands of thread 134 (e.g., nylon) (FIG. 2) are sewn through the array 102a and around the flexures 124 in order to prevent the conductive regions 128 from slipping out of alignment with the electrodes 118a-118d. 
Referring back to FIG. 2, each internal flexure 136 is connected at its distal end to one of the flexures 124, the deflecting mechanism further including a transverse ribbon 138 that extends between the distal portions of the internal flexures 136. The transverse ribbon 138 is preferably pre-shaped such that when in the relaxed condition the ribbon assumes the corrugated configuration and such that when in a compressed condition it is folded along the plurality of creases 140 that extend along its length. Flexures 124 and 136, and ribbon 138, are preferably made of an insulated spring material, such as heat treated 17-7 PH stainless steel.
Turning to FIGS. 4A-B, the electrode array 102a further includes a pair of broad faces 112 spaced apart from one another when the array 102a is expanded and tensioned by the deflecting mechanism 102b (FIGS. 2, 3A and 4A). The entire applicator head 102 is preferably coated with a dielectric material coating, such as parylene. Narrower side faces 114 extend between the broad faces 112 along the sides of the applicator head 102, and a distal face 116 extends between the broad faces 112 at the distal end of the applicator head 102. Insulating regions 110 are formed on the applicator head to divide the mesh into four electrodes 118a-118d by creating two electrodes on each of the broad faces 112. To create this four-electrode pattern, insulating regions 110 are placed longitudinally along each of the broad faces 112 as well as along the length of each of the faces 114, 116.
During use of the ablation system 100, distal and proximal grips 142 and 144 forming the handle 106 are squeezed towards one another to withdraw sheath 104 and deploy the applicator head 102 (FIG. 1B). This action results in relative rearward motion of the outer hypotube 120 and relative forward motion of the inner hypotube 122, causing deflection of flexures 124 and 136, thereby expanding and tensioning the electrode array 102a (FIG. 2). The deflecting mechanism 102b formed by flexures 124, 136, and ribbon 138, deploys the electrode array 102a into a uterine shape. Although the ribbon 138 of the deflecting mechanism 102b further maintains electrodes 118a-118d separated and insulated from each other during use of the system 100, the ribbon 138 is usually not adapted to further assist the distal face 116 of the electrode array 102a to contact a uterine fundus.
Accordingly, it would be desirable to provide for a simple deflecting mechanism for maintaining contact of the electrodes with the uterine fundus. Additionally, where expensive materials are used (e.g., materials of the flexures), or expensive or complex manufacturing techniques (e.g., deflecting mechanism and handle), it would be desirable to limit the quantity of these materials or complex manufacturing techniques, and provide for an ablation system as inexpensive and simple to manufacture as possible, while being well-suited for performing endometrial tissue ablation procedures.